1. Field of the Invention
The present invention relates to a highly versatile system for providing desired types of connections between first and second components or parts of a mechanism or machine, wherein a hole or other form of "aperture" is formed through the first component, wherein a portion of the second component projects relatively loosely through the aperture, wherein elastomeric material extends perimetrically about the second component to substantially "fill" a confined, ring-like space that is defined within the aperture of the first component, and wherein the elastomeric material is securely clamped and compressed within the confined, ring-like space to provide a desired type of connection between the first and second components, namely a connection that permits very little, if any, relative movement to take place between the connected components.
A more particular need that is addressed by the preferred practice of the present invention relates to the provision of a novel and improved method and means for securely connecting apertured components and elongate rods or shafts-- i.e., a system for providing connections that are sufficiently reliable for use in mounting components as such as gears, pulleys, rollers and the like on shafts. In preferred practice, the present invention relates to a method and means for clamping elastomeric material in a confined annular space that is provided between the inner diameter of a bore or mounting hole that is formed through a component such as a gear or a pulley, and the outer diameter of a shaft that extends loosely through the bore-- with the clamped elastomeric material typically including one or a combination of sleeve-like and/or O-ring-like members that are "hydro-elastomerically" compressed within the confined annular space so as to assist in providing a highly reliable driving connection between the shaft and the shaft-mounted component.
2. Prior Art
Pulleys, gears and other components that are "apertured" (meaning that they are provided with "bores" or "mounting holes" that extend through the components to define passages that are intended to receive elongate support members such as shafts, rods and the like) are well known and take a variety of forms. Typically, such pulleys, gears and other components are formed from rigid materials such as metal or plastic, or from combinations of metal and plastic.
The subject of forming apertured components such as gears, pulleys and the like from combinations of rigid materials as by utilizing metal "inserts" that have portions that are at least partially encompassed by or embedded within in plastics materials has been addressed by prior proposals. For example, this subject is addressed by the inventions of U.S. Pat. No. 4,722,722 and 4,946,427 issued Feb. 2, 1988 and Aug. 7, 1990, respectively, to John F. Rampe (referred to hereinafter as the "Referenced Pulley Patents," the disclosures of which patents are incorporated herein by reference). In accordance with the preferred practice of the inventions of the Referenced Pulley Patents, a component that is to be mounted on a "shaft (typically a gear or a pulley) is formed by molding plastics material in situ about perimetrically extending portions of a metal "insert." The "insert" defines at least a portion of a "hub" formation that has a bore extending centrally therethrough to provide a passage that is suited to receive a shaft onto which the component will be mounted and drivingly connected so as to be movable with the shaft.
In a typical application wherein an apertured component (e.g., a pulley of the type that is formed in accordance with the Referenced Pulley Patents) is to be mounted on a shaft, the inner diameter of the bore of the component typically closely receives the outer diameter of the shaft onto which the component is to be mounted. In conventional practice, the bore receives the shaft in a slip fit so that no significant amount of ring-like space is provided between the inner diameter of the bore of the component and the outer diameter of the shaft (i.e., the component does not "loosely" receive the shaft onto which the component is to be mounted). To complete the connection of the component to the shaft, one or more commercially available fasteners (such as set screws that are threaded through appropriately configured holes, drive pins that extend through appropriately configured holes, keys that extend in appropriately configured keyways, or the like) are used to hold the component in position on the shaft such that a secure driving connection is provided between the shaft and the shaft-mounted component that prevents relative rotation therebetween when torque forces need to be transmitted between the shaft and the shaft-mounted component.
The use of keys positioned in keyways, and of splined-type connections to couple components such as pulleys and gears to shafts tends to be expensive in that it normally requires precise machining so that suitably configured keyways or mating spline formations are provided both on the shaft and on the component that is to be mounted on the shaft. If a semi-circular shaped keyway is provided on the shaft to receive what is known in the art as a Woodruff key, or if a groove-like keyway of limited length is machined on the shaft, any needed axial repositioning of a rotary drive component relative to the shaft may require the machining of an alternately located key-way, or the machining of an extension of an existing key-way or spline formation--which often means that the shaft must be removed and/or replaced with a properly reconfigured shaft. Thus, in many applications the use of these types of connection systems limits the extent to which shaft-mounted components can be positioned or repositioned axially along a shaft.
Moreover, while the use of keys positioned in keyways or the use of mating spline formations may provide effective ways in which to address the need for preventing relative rotation between shaft-mounted components and the shafts on which the components are mounted, the provision of keys in keyways or of mating spline formations does not address the very real companion need to prevent relative axial movement of shaft-mounted components and the shafts on which the components are mounted. Prevention of relative axial movement typically is addressed in conventional practice as by using set screws, pins, cotter pins or the like that are positioned in suitable holes formed in the components and/or in their mounting shafts, or by using other types of commercially available fasteners such as snap rings that are positioned in grooves that are machined in the shafts--with many of these connection techniques also serving to limit the extent to which the positions of components easily can be adjusted axially along the shafts on which the components are mounted.
One relatively non-conventional approach that has been utilized with success to mount rotatable components such as gears and pulleys at desired positions extending axially along shafts is addressed by U.S. Pat. No. 3,830,577 issued Aug. 20, 1974 to John F. Rampe et al (referred to hereinafter as the "Referenced Pulley Mounting Patent," the disclosure of which is incorporated herein by reference). The unique approach that is taken in accordance with the preferred practice of the invention of the Referenced Pulley Mounting Patent involves a plural step procedure that, in a simple way, addresses not only 1) the problem of preventing relative rotary movement between a component (typically a gear or a pulley) and the shaft on which the component is mounted, but also 2) the problem of preventing relative axial movement between a component and the shaft on which it is mounted, and 3) the need to provide a ready capability to selectively position and reposition a component axially along a shaft on which the component is mounted.
In accordance with one form of preferred practice of the invention of the Referenced Pulley Mounting Patent, the component that is to be mounted on a shaft is provided with a generally cylindrical hub formation, with the hub formation having an inner diameter that closely receives the outer diameter of the shaft (typically in a slip fit), and with the hub formation having an outer diameter that extends substantially concentrically about the inner diameter. A substantially radially extending hole is formed through the hub, with the inner end of the hole opening through the inner diameter, and with the outer end of the hole opening through the outer diameter. A pointed pin, typically formed from hardened steel, is inserted into the hole, with the pin having its pointed end projecting inwardly for engaging the outer diameter of a shaft on which the component has been positioned, and with the pin having a relatively flat (i.e., non-pointed) outer end that extends radially outwardly beyond the outer diameter of the hub. An endless clamping band is loosely installed about the outer diameter of the hub, with the band not only surrounding the outer diameter of the hub but also encompassing and engaging the outer end of the pin. The clamping band is progressively clamped so as to diminish the diameter of the area that it surrounds, with this clamping preferably being effected as by crimping portions of the band toward each other at a location that preferably is on the opposite side of the hub from where the outer end of the pin projects through the outer diameter surface of the hub. As the clamping of the band continues, the band eventually is brought into firm clamping engagement with the outer diameter surface of the hub formation. This progressive clamping of the band serves to drive the pointed pin radially inwardly such that its pointed inner end penetrates the material of the shaft to establish a secure "pinned" type of driving connection between the rotatable component and the shaft on which the component is mounted.
The character of the "pinned" type of connection that results from the use of the preferred practice of the invention of the Referenced Pulley Mounting Patent tends to prevents both radial and axial movement of the component relative to its mounting shaft. Moreover, the component initially can be positioned at substantially any desired location along its mounting shaft; and, if axial repositioning is desired, the clamping band and the pointed pin either can be loosened or removed and/or replaced to permit repositioning to be effected.
The use of set screws, pinned type connections, and many other previously proposed forms of couplings that typically utilize a variety of commercially available fasteners to securely connect rotary components such as gears and pulleys to shafts often tend to cause stress concentrations to develop, with the result being that, in many instances longevity of service of the resulting component-to-shaft connections is diminished due to such factors as "fatigue" and/or stress-induced breakage.
A difficulty that often must be dealt with in providing component-to-shaft connections is that of maintaining concentricity (i.e., of assuring that the center axis of a shaft-mounted component extends coaxially with respect to the center axis of the shaft on which the component is mounted). The use of set screws and other conventional fastening devices often tends to hinder the attainment of this objective. For example, as a set screw is tightened in a threaded, radially extending hole that is formed in a hub portion of a pulley so as to bring the inner end of the set screw forcefully into engagement with one side of the outer diameter of a shaft on which the pulley is positioned, the tightening of the set screw into secure engagement with the shaft tends to move the pulley (and hence its center axis) to one side of the center axis of the shaft and/or to skew the center axis of the pulley relative to the center axis of the shaft--whereby the objective of maintaining concentricity is defeated.
The principal way in which the difficulty of maintaining concentricity of shafts and shaft-mounted components has been addressed in the prior art is to assure that a snug, precision fit is achieved as a shaft-mounted component is brought into a desired position along a shaft on which the component is to be mounted. Typically, this has called for at least some machining to be done on one or both of the component and its mounting shaft, with the result that the forming of component-to-shaft connections that are quite precisely concentric has typically been a costly objective to achieve.
Turning to a different but related subject, there exists in the art an increasing need for a capability to "resiliently connect" some components of mechanisms or machines, and to "cushion mount" rotary drive components such as gears and pulleys on shafts, with the resilient nature of the resulting mountings providing connections that are essentially "rigid" except that, to a very limited extent, provision is made for minor relative movements of the connected components. For example, as efforts increasingly are being made to reduce the noise that is made by office machines such as impact printers, efforts are being made to "resiliently connect" and/or to "cushion mount" some otherwise rigidly connected components--with the objective in mind of diminishing the transmission of objectionable noise between components that are, in essence, rigidly connected. By way of another example, in some mechanical equipment such as impact printers, it has been found that shock absorbing mountings of certain components can prevent the transmission of unwanted vibration-causing forces between components that are, in essence, rigidly connected--whereby longevity of service life of the equipment may be significantly enhanced, and objectionable noise that otherwise would be generated by the equipment tends to be damped. However, prior pulley-to-shaft connection system proposals and the like have not tended to adequately address these needs and/or have provided unduly complex and expensive-to-implement proposals that have left open the need for improved proposals exhibiting good performance at relatively low cost.
In conjunction with shafts and rods that move relative to surrounding components (i.e., shafts and rods that are not rigidly connected to their surrounding components--for example, in applications involving piston rods that project from and move axially with respect to housings that surround portions of the piston rods), it is well known to use resilient sleeve-like or ring-like members formed from elastomeric materials to provide "seals." Examples of such sealing devices are provided by what has become well known to those who are skilled in the art as "O-rings." In some instances, such seals prevent the escape of fluid such as hydraulic fluid or compressed air, or the entry of ambient water vapor or sea water. In other instances, the seals serve to retain lubricant within selected regions that extend axially along shafts, piston rods and other elongate members that move relative to surrounding supporting structures. In still other instances, the seals minimize the entry of contaminants such as dust, metal filings, chemical vapors and the like into selected regions that extend axially along shafts and piston rods.
However, to the extent that prior proposals have utilized ring-like and/or sleeve-like formations of elastomeric material extending about shafts, piston rods and the like, the elastomeric material has not been so "compressed" as to positively prevent significant relative movement from taking place between shafts or piston rods and such supporting and/or surrounding structures as may extend circumferentially about the shafts and piston rods. To the contrary, in accordance with prior proposals, sleeve-like and/or ring-like formations of elastomeric materials typically have been used more to "promote" than to "hinder" relative movement from taking place between shafts or rods and such structures as extend circumferentially about the shafts or rods.
Thus, while conventional practice has made use of sleeve-like and/or ring-like members 1) that are formed from elastomeric materials, 2) that are positioned to extend circumferentially about portions of shafts or rods, and 3) that are interposed between shaft or rod portions and rigid structures that extend circumferentially about such shaft or rod portions, it is quite appropriate to observe that the uses that have been made of such elastomeric members have judiciously "provided for" and "permitted" (indeed, often "facilitated") the capability of the shafts or rods to move rotatably and/or axially relative to surrounding structures. It therefore "flies in the face" of conventional practice to deploy sleeve-like and/or ring-like members 1) that are formed from elastomeric materials, 2) that are positioned to extend circumferentially about portions of shafts or rods, and 3) that are interposed between shaft or rod portions and rigid structures that extend circumferentially about such shaft or rod portions, with the purpose in mind to use the elastomeric members to "prevent" (i.e., to "foreclose" the capability of) the shafts or rods from moving rotatably and/or axially relative to the surrounding structures.
Moreover, prior proposals have not taught or suggested the use of a "hydro-elastomeric" approach (i.e., an approach wherein elastomeric material is subjected to such extensive compression force as to bring out substantially "fluid-like" behavior characteristics that are used to advantage, while enabling the elastomer to retain many of its "solid-form" behavior characteristics that also are used to advantage) to address the problem of providing secure connections between mechanical components such as shafts and shaft-mountable components such as gears, pulleys, rollers, wheels and the like. Nor have prior proposals pointed to the highly advantageous use that can be made of a "hydro-elastomeric" approach to address the very real need that exists in the art for a versatile connection system that can be used to form secure connections that are, in essence, "tailored" to exhibit characteristics that are chosen from a wide range of available design characteristics--examples being connections that range from "substantially rigid" (i.e., connections that permit little if any relative movement between components that they couple) to connections that can be thought of as being relatively "resilient" or "cushioned" in character (i e., connections that do permit, to a limited extent, relative movement between connected components, and that often can be deployed advantageously to damp vibration, to absorb shock and/or to diminish noise transmission).
In summary, while the prior art is replete with proposals for connecting components of mechanisms and machines, prior proposals have not recognized that significant advantages can be achieved by utilizing a "hydroelastomeric" approach to simultaneously address such needs as 1) needs for preventing or permitting, to desired degrees, selected types of relative movements between connected components; 2) needs for providing or permitting a capability to selectively position and reposition components that are to be connected; 3) needs for preventing the buildup of undesirable stress concentrations as the result of providing component connections; and 4) needs for providing connections that can be designed to select from a wide range of available "connection behavior characteristics" that includes not only a capability to limit relative movement between connected components but also to provide shock absorbing, noise abating and/or vibration damping mounts that are "tailored" to conform to needs of particular applications, to enhance longevity of service and improve overall performance.